Gerald, the ruby stones are available in different grits. The two I
use are a coarse one that cuts a surface on the graver fairly
quickly, and a fine one that is indeed, as you say, a good substitute
for polishing papers, but differs in that, being very flat, your
graver surface can also remain flatter than is sometimes the case
with, say, 4/0 paper. The fine ruby stones do cut faster than the
papers. It’s easy to refine a point already shaped with the coarse
stones, on the fine one, despite the difference in coarseness.
As to grindings getting imbedded in the stone, well, sort of. The
things are quick and easy to clean when they do get a bit dirty, and
using a tad more oil keeps the grindings “floating” a bit too. I
don’t find the residue from use to be a problem at all.
The big advantage of the ruby stones is simply their durability and
hardness. They’re dense enough that even years of use don’t damage
the flatness of their surfaces. The ones on my bench have been in use
now for well over 20 years, and remain as fast cutting and flat and
true as when I bought them.
Now, I’ll grant, a good traditional stone is probably a little bit
faster cutting. That open grain structure tends to do that. And being
porous, they’re more self lubricating what with absorbed oil and all.
But they get grooved, dished, worn, etc, with use. The ruby stones
simply don’t seem to do so.
But of course, much of this is a matter of taste and preference. If
you’re used to using traditional sharpening stones, the ruby stones
might feel a little unfamiliar or odd, and the reverse is true if
you’re used to the ruby stones, or yet other systems, like diamond
sharpening “stones” (really fast cutting, and can be used with
carbide gravers too. But might not be as long lasting. Depends on
type and how treated, etc. )